1. Field of the Invention
The present invention relates to apparatus for dispensing measured quantities of a liquid such as milk or fruit juice into an open top container.
2. Description of the Prior Art
One common type of container in which liquid food products such as milk and fruit juices are sold is a gable top carton made of paperboard or the like which has heat sealable top and bottom closure panels. In general, this type of carton is made of a high grade paperboard stock which is coated on both sides with a thermoplastic material such as polyethylene. The polyethylene coating on the paperboard is used for moisture-proofing, and is also a heat and pressure sensitive adhesive used to seal the top and bottom closure panels of the carton to make it liquid tight.
Automatic machines have been developed which erect flat, collapsed cartons of this type, form and seal the bottom ends of the carton, fill the cartons with the liquid product, and form and seal the top ends of the cartons. These machines generally include a rotatable mandrel assembly which is driven in a step-by-step indexing motion. The flat, collapsed cartons are withdrawn from a magazine, erected into an open-end tubular form and loaded onto each mandrel. As the mandrel assembly is rotated, the carton blank on the mandrel is sequentially advanced to work stations at which the bottom closure panels of the blank are broken, the bottom is heated, and the bottom is closed and sealed. Finally, each carton blank, with its bottom end sealed and its top end open, is withdrawn from its mandrel and deposited on a conveyor line. The cartons on the conveyor line are advanced through a top breaker unit at which the top panels are broken, a filling area at which the cartons are filled with the desired quantity of liquid, a defoamer area at which foam generated during the filling of the liquid is removed, a top heater area at which the polyethylene coating on the carton is heated, a top folding area at which the top panels are folded, and a top sealing area at which the tops of the cartons are sealed.
Examples of machines of this general type are shown in U.S. Pat. Nos. 3,088,380; 3,153,374; 3,405,505; and 3,669,160; and in British Pat. Nos. 709,454; 1,001,595; and 1,001,596.
One important portion of this type of machine is the carton filling apparatus, which must provide precisely measured quantities of the liquid into the containers at a high rate consistent with the cycle rate of the machine.
The carton filling apparatus used in prior art machines typically includes a fill tank reservoir for holding the liquid product, a vertically oriented piston and cylinder, a fluid passage from the tank to the cylinder, and a passage from the cylinder to a dispensing outlet. A valve arrangement controls flow from the tank to the pumping chamber formed by the piston and cylinder and flow from the pumping chamber to the outlet.
In one type of prior art system, a rotary valve arrangement is used. In one position, the rotary valve connects the tank to the pumping chamber so that the pumping chamber can draw liquid from the tank. In the other position, the rotary valve connects the pumping chamber with the outlet so that the movement of the piston discharges the liquid within the pumping chamber into the carton.
Another commonly used valve arrangement includes a pair of spring loaded check valves. One check valve is arranged between the tank and the pumping chamber, and the other check valve is located at the outlet. One disadvantage of spring loaded check valves is that pressure of the liquid product is required to open the check valve at the outlet, and the liquid then has to be squeezed through that orifice. In the process of opening the check valve at the outlet, the liquid velocity created generates foam. This foam subsequently must be removed so that proper sealing of the top ends of the cartons can be achieved.
Because the product being dispensed is a food product, rather stringent cleaning procedures are necessary for health reasons. The cleaning procedures normally are of two types: cleaning in place and disassembly for handwashing. It is general practice in the dairy industry, for example, to clean the fill apparatus in place on a daily basis. This involves cleaning the fill apparatus without disassembling it by running a cleaning solution through the fill apparatus. In addition, it is common practice to systematically disassemble the fill apparatus on some sort of routine. Since most machines have multiple outlets for filling cartons in stages, it is common to disassemble and handwash the various individual fill assemblies on a rotating basis.
One continuing problem with prior art fill apparatus has been the ability to thoroughly clean the apparatus "in place". O-rings, which are commonly used as part of the valve mechanisms of prior art fill apparatus are not fully cleanable in place because of the possibility of product or contaminants getting behind the O-rings and making it difficult to clean behind those areas. In addition, the various components of spring loaded check valves, including retainers of the valves and valve seat all provide ideal hiding places for bacteria to grow.
Still another disadvantage of the prior art fill apparatus has been that the connection between the bottom of the fill tank and the outlet has normally been rather long (18 inches or more). Not only does this increase cost, since these connections normally are of expensive stainless steel, but it also increases the area at which bacteria can grow and which must be cleaned.
The prior art fill apparatus has typically been rather complex to disassemble, hand-clean and then reassemble. As a result, disassembly and handcleaning of the prior art fill apparatus has been time-consuming, and thus the frequency of disassembly and handwashing has typically been minimized.
There is a continuing need for improved fill apparatus for use in machines which fill cartons with liquid food products such as milk and fruit juices which is easily cleaned in place, has a minimum number of areas which bacteria can grow, and which has a minimum number of parts which can be easily disassembled and handcleaned.